Piston expander



Patented Feb. 15, 1944 UNITED STATES PATENT OFFICE PISTON EXPANDERHarold K. Switzer, Newport, Ky. Application August 3, 1940, Serial No.350,426

(Cl. Sil-) 4 Claims.

This invention relates to the art of expanding or reshaping pistonswhich are of improper size. In the operation of internal combustionengines the pistons may become collapsed or misshapen due to therepeated expansion and contraction to which they have been subjectedover a period of time under varying temperature conditions.

The looseness which results from the collapse and distortion of thepiston is objectionable for several reasons. The efficiency of theengine is substantially decreased by pistons of improper size or shapeand the objectionable piston slap commonly heard in older engines, is acharacteristic symptom of the defect.

'I'his invention is particularly directed to a simple, inexpensive handtool for expanding pistons by rapid and easy manipulation of the toolrelative to the piston. pistons in which this tool may be utilized isfully described and claimed in my United States Patent No. 2,289,941 ofJuly 14, 1942. Heretofore, complex peening machines have been utilizedfor the reshaping operation. It has been necessary to dismantle theengine and remove the pistons from it before they could be operated uponin the peening machine, and the entire job is both expensive andtedious.

In contrast, the principal object of the present invention has been toprovide a Very simple tool with which the pistons can be operated upon,reshaped and expanded while they are in the engine or after they havebeen removed from it.

Briefly, the present invention contemplates a tool by means of which thematerial of the piston series` of lines extending longitudinally of thepiston skirt. The metal of the skirt along these lines of pressurecontact is swaged, and peculiarly the piston is thereby expanded. In atypical expanding operation, the portion of the skirt opposite thethrust side of the piston is worked upon to accomplish the reshaping ofit; however other parts of the piston also may be treated forotherreshaping or expanding purposes.

For use in the practice of the method described and claimed in myaforesaid patent, this invention contemplates a simple and inexpensivetool which may be employed satisfactorily by an ordinary automobilemechanic. This tool includes a pair of hardened metal wheels. One of thewheels is flat peripherally and is of substantial width. The other maybe relatively thin and the periphery may be rounded. The two wheels arearranged to cooperate with one another to exert a skirt is contactedunder pressure along a` 'taken on a line through the piston skirt at theswaglng action'upon the metal of a piston skirt placed therebetween.

The tool normally is used so that the thin wheel rests on the interiorsurface of the piston skirt, and a handle is provided for the tool sothat the wheels 'may be moved along lines 1ongi` tudinally of the skirtto compress the metal; it isy thiscperation which expands the skirtcircumferentially. v Y v Except in extraordinaryinstances the toolisused to operate upon the pistons without dismantling them from theengine block, for instance with the oil pan and the connecting rodbearings removed the piston whichis to be operated upon is drawndownwardly to a polntlat which the skirt of it is disposed beneath theblock; the skirt is now accessible and readily may be reshaped andexpanded. f

The tool may be used with substantially all types of pistons, forinstance those made of cast iron and semi-steel as Well as those madefrom aluminum alloys. The operation of expanding or reshaping a pistonrequires but a fraction of the time required by past methods.

For use in conjunction with the tool, an object of the present inventionalso has been to provide a shieldadapted to be fitted around the pistonskirt so as to keep the outer roller of the tool from marring the metalsurface as the reshaping operation is performed-l In the use of such aprotector the major swaging action is accomplished by the thin wheel atthe interior of the piston. In other instances it is also practiced, bymeans of the present improvement,to expand the piston to an oversizedimension and then machine it back to size as in a lathe.

In the drawings:

Figure 1 is a perspective View showing a piston in the process of beingexpanded by a hand tool made according to the present invention;

Figure 2 isa fragmentary cross sectional view point where the toolisacting;

Figure 3 is a side View of the hand tool shown inFigure 1 wherein thedetails of construction are shown in cross section;

Figure 4 is a perspective View of a guard `which may be utilized toprotect the piston against marring by the tool;

Figure 5 is a fragmentary cross sectional view taken longitudinallythrough the piston;

Figure 6 is a View similar to Figure 5 in which the tool has beenmodified slightly to accommodate a piston having a strengthening ridgerunning around the inside of the piston near the lower edge of theskirt;

Figure 'l illustrates a modified form of the tool in which a stationaryswage block is utilized in place of the thinner roller;

Figure 8 is a cross sectional view taken on line 8-8 Figure '7, furtherillustrating the modification.

Figure 9 is a diagrammatic cross sectional View taken laterally throughone of the cylinders of an internal combustion engine illustrating themanner in which a piston may be expanded without removing it from thecylinder.

Figure l0 is a cross sectional View taken on line Ill-I0 of Figure 9.

In the drawings the piston shown is a relatively typical aluminum alloypiston having a` The use ofthe tool with other T slot in its skirt.types of pistons will be discussed at a later point in the description.The thin-walled portion of the piston, termed the skirt, is indicated atl5.

The tool illustrated in the drawings, comprises twoarms I6 and I1.Thearms aresecured to a bracket I8- by nutswhich engage threadedportions I9 extending through holes in the bracket from the ends ot theThe arms extend substantially parallel bracket.v The bracketis bentdownwardly at an angle to the arms, as at 20, and is secured to ahandle- 2| by a screw or other means.

Apair of `wheels 22 and 23 is mounted in slots inthe ends of the armsrespectively. The wheels arefjournalled Aonpins 24'press fitted inappropriate holes inthe respectiveends ofthe brackets. One of rowi and.rounded peripherally while the other, indicated iat 23, is wide andflat peripherally.

Medially ofthe length of the arms means is provided for adjustingthearms` toward and from one another. The adjustment means comprises ascrew `25'which is threaded intoone of the arms andv-locked therein by athreaded collar 26. The screwH extends at right angles to the arm andpasses througha'hole in the other arm. Beyond the second arm nut 21.Thus, by tightening the thumb nut the two arms are drawn together. Aslight exing or springiness inthe arms I6 and I1 aids materially inproducing a vsmooth operation of the tool.

A shield'28, shown in Figure 4, comprising a thin sheet of'spring steelm-ay be utilized to keep the outerwheel from marring the outer surfaceof the piston. The shield is placed around the skirt ofthe piston and isretained in placev by its own spring action. In most instances, theshield is' not necesssarythough it maybe used as a special precautionagainst marring the surfaceof the piston.

Operation The expansion operation may be performed, as has been thepractice heretofore, byremoving the piston from the. cylinder. In thisinstance, the piston is clamped orheld headdown on the work bench. Whenused on aluminum alloy types of piston, the wheelsA are first rolled upand down the skirt on both sides ofthe slot as near the pin bosses as ispractical. The wheels should be rolled longitudinally of the pistonsv instraight lines, with the thinner wheel on the inside of the piston.After each stroke, the tool is moved nearer the slot. It is onlynecessary to swage van areafof approximately 3A; of an inch from eachpin b`oss. Five or six strokes of the tool are thus sufficient to expandthe piston about four to six toone another from the thewheels, indicatedat 22, isnarthe screw is engaged by a thumb `the wheels; bowing outone-thousandths of an inch. The tool should be adjusted so that thewheels exert only a light squeezing pressure on the metal of the pistonskirt since it is not necessary or desirable to gouge the metal toexpand pistons by this method.

This same procedure may be used on semisteel pistons as well as otheraluminum pistons, that is, swaging the skirt of the piston near the pinbosses on the side oppositethe one subjected to thrust.

Cast iron pistons react somewhat differently to the swaging action ofthe method than do aluminum alloy pistons. Cast iron expands beneathwhere the wheels are rolled. Cast aluminum pistons expand at the slot,that is, the collapsed section of the skirt near the slot is reshaped byswaging the areas on both sides of the slot adjacent the pin bosses. Camground pistons which have become rounded through use may be reshaped byswaging the metal of theskirt in these same areas, that is, near the pinbosses. This causes the cam.4 groundpiston to reassume its slightly ovalshape. To reshape a cast iron piston,y the wheels are.rol1ed over theskirt in the area directly opposite the center of thrust. Cut-away skirtpistons or slipper pistons made of cast iron. are also reshaped bythislatter method of employing the tool.

Certain pistons having a rib around the inside of. the piston below thepin bosses require .a slightly modified tool, (Figure-6). In thisinstance the thinner wheel is journalled off-center of the arm so thatthearm clears the rib. Referring to Figures 7 and 8, a modified form ofthe thin swaging wheel isshown.. Herea swage block 29 is substituted.The block is secured inv a slot in the. end of one of the arms, by a pin3D; The operating surfaceoi the block comprises a rounded ridge 3lsimilar to the rounded peripheral ridge of the thin swaging'wheel.y

A practical advantage of .considerable importance provided' by thepresent invention is that pistons mayin many instances be expanded4without removing them completely from the cylinders. The manner inwhich this is accomplished. is disclosed in Figures 9 and 10. Thispractice is not applicable in the cases of V-type or radial engines. Toprepare the piston, the oil pan and the connecting rod bearings areremoved. The piston to be treated is then pulled down to expose theskirt and the connectingrod and crankshaft are moved to one side asshown in Figure Y 9. In most engines, the piston can be brought down tovreston the throws of the crankshaft as shown. They expanding operationcan then be carried out asv described above.' The piston may be slippedback up into place to check the fit as the expanding operation proceeds.

In some cases, the handleof the tool interferes with the operation ofthetool because of' obstructions. In these instances, the handle. can bereversed by changing the position of the arms I6 and I1.

skillful and judicious use of it, the piston skirtY may be squeezed orthinned to the desired degree, thus creating compensatory expansion ofthe piston skirt so that it better ts the cylinder.

The tool is susceptible toy 2,341,959 3 Having described my invention, Idesire to be said rollers being adapted to exert a squeezing limitedonly by the following claims: action on the piston skirt, one of saidrollers 1. In a piston expanding tool having a handle having anoutwardly tapered tread for the dismetal swaging elements carried one byeach of tread for supporting the portion of the skirt opsaid arms; oneof said metal swaging elements posite to that with which the rst namedroller a narrow rounded tread for engaging the piston 10 4. In a toolfor expanding a piston by swaging surface. the skirt of the piston alonglines extending 1on- 2. In a piston expanding tool, a pair of armsgitudinally of said skirt a pair of spaced arms spaced apart andconnected adjacent one of their adapted to straddle a piston skirt, aswaging elerespective ends, a metal displacing element cai'- mentcarried by each of said arms, one of said ried by each of said arms,sala elements being 15 swaging elements presenting a narrow treadsuradapted to engage the skirt of a piston on opface for displacement ofthe metal in the piston each of said arms with its axis transversethereto, HAROLD K. SWITZER.

